/Engine/Plugins/MeshPainting/Source/MeshPaintingToolset/Public/TexturePaintToolset.h
Keep old legacy method of initializing render target data for the paint brush texture;
static void SetupInitialRenderTargetData ( [UTexture2D](API\Runtime\Engine\Engine\UTexture2D) * InTextureSource, [UTextureRenderTarget2D](API\Runtime\Engine\Engine\UTextureRenderTarget2D) * InRenderTarget )